As an example of display devices, a display device in which a backlight unit of a white light source and a liquid crystal display panel comprising a primary-colors filter are combined is well known. Since the color filter permits a specific wavelength range to pass therethrough and cuts the other wavelength ranges, the efficiency of the light emitted from the backlight unit is deteriorated by the cut wavelength ranges in the display device.
In contrast, a display device in which a backlight unit of a single-color light source and a liquid crystal display panel comprising a wavelength conversion element are combined has been disclosed. In a quantum dot of a semiconductor, for example, light-emission properties such as a polarization direction and a peak wavelength can be varied by controlling its shape and size. For this reason, application of such a quantum dot to a wavelength conversion element has been expected.